Monday marked the beginning of an important trial in France. Four men, aged from 23 to 30 years, stand accused of attempted murder for their part in a story that stretches back to 2007, when violent clashes paralysed the Parisian suburb of Villiers-le-Bel.

The violence was sparked by a tragic accident that saw two young people lose their lives when their motorbike collided with a police car. This tragedy – the circumstances of which remain unclear – provoked three days of rioting. Although unlike 2005, when riots spread to all corners of the country, the violence in Villiers-le-Bel went no further than the neighbouring suburbs. However, the intensity of the violence reached a whole new level: it was the first time that firearms were widely used against the police in this context. During the riots approximately 90 police officers were injured, some seriously.

Following the riots, President Sarkozy put pressure on the forces of order, telling them to use whatever means necessary to ensure that these crimes did not go unpunished. The police took him at his word. On 18 February 2008, about 1,500 police officers carried out a raid on the housing estates in Villiers-le-Bel. The police had a list of names and arrested 33 people. In July 2009, 10 of those arrested received sentences of one to three years. Five more will be sentenced at the end of this trial.

The trial has aroused huge media interest in France, not least because it is the first time in French history that anybody has been tried for shooting at policemen. However, it is the unconventional way in which the accused have reached the courtroom that raises the most questions. Following the 2008 raid in Villiers-le-Bel, it emerged that the interior ministry had offered a reward and a guarantee of anonymity in exchange for information on the riots. In other words, the state paid residents of Villiers-le-Bel to denounce their neighbours for cash. Hardly the most reliable of methods in an area characterised by low revenues and unemployment. More significantly, of the young people interviewed, some claimed that the police had ordered them to provide names to avoid facing prison on trumped up charges. The last time such methods were used was under the Vichy regime.

Somewhat paradoxically, this attempt to find justice for the injured policemen is completely undermining the credibility of the authorities, and of the case itself. The injured policemen have never been able to identify their attackers – the riots took place at night for the most part and involved hundreds of people. So the case rests almost solely on the testimony of these anonymous informants, testimony that essentially was bought by the state. But even this has become uncertain. Certain informants changed their statements in the run-up to the trial, while others were simply retracted. None of this has quelled the enthusiasm of the prosecution.

President Sarkozy has, since his days as interior minister, always advocated a hard-line approach to crime. He has repeatedly promised to rid the suburbs of the "thugs" and "delinquents" who hold sway in these areas. The four men in the docks represent the culmination of this campaign. But this "justice" has a hefty price tag attached, literally. The means used by police to identify these suspects were highly questionable. Of course, the affair has shown that money talks, but that doesn't necessarily mean it speaks the truth.

Ultimately, four men are facing life in prison – a fifth stands accused of assisting them – without a shred of tangible evidence against any of them. Since their arrest, Respect, Truth, Justice, a local association, has supported the men. The name of the association is ironic here, since these qualities do not appear to be very high on the agenda.